Abstract
A Monte Carlo (MC) molecular model, with parameters derived from density functional theory calculations, is used to describe experimental data for the rate of ethane hydrogenolysis for a Pt/SiO2 catalyst over a wide range of conditions. The surface concentrations of the most abundant stable species (hydrogen atoms, ethylidyne species, and di-σ-bonded ethylene) are simulated with a MC grandcanonical ensemble, and the rate of ethane hydrogenolysis is calculated by simulating surface concentrations for three types of transition state complexes for C−C bond cleavage. The simulation shows that larger repulsive interactions between adsorbed C2Hx and H species lead to more negative reaction orders with respect to the hydrogen pressure. The results of the MC simulation indicate that the reaction proceeds primarily through C−C bond cleavage in adsorbed C2H5 species, with smaller contributions from adsorbed CHCH3 and CHCH2 species. The MC results suggest that although the most abundant surface hydrocarbon species has a stoichiometry of C2H3, the reaction proceeds through more highly hydrogenated C2H5 species. The state of the surface is predicted to change from being primarily hydrogen-covered at most experimental conditions to being highly hydrocarbon-covered at low hydrogen partial pressures.
Published Version
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